The present invention is directed to a three pole safety switch and a mating connector and, more specifically, to a three pole, plunger switch having a terminal configuration that insures proper alignment of the plunger switch and the mating connector during mechanical connection.
Plunger switches are widely utilized in many diverse applications including use as safety switches in various motorized devices. For example, U.S. Pat. No. 5,424,502, issued Jul. 27, 1993 to Williams, entitled QUICK-INSTALL SEAT SWITCH and assigned to the assignee of the present invention discloses a plunger switch and quick install mounting assembly for mounting the plunger switch on a rigid seat pan of a garden or lawn tractor. The ""502 patent is incorporated herein in its entirety by reference. The switch assembly disclosed in the ""502 patent is a single pole plunger switch. The switch has two terminal contacts, the plunger switch electrically coupling or decoupling the two terminals depending upon the plunger or actuator position. The mounting assembly of the ""502 patent allows the plunger switch to be connected to the seat pan such that the actuator of a switch installed on a seat pan extends above the seat pan and the switch housing is below the seat pan.
In the mounting assembly disclosed in the ""502 patent, a cover overlies the actuator. When the operator is seated on the seat cushion, the cover is forced downward by the deflection of the seat cushion thereby depressing the actuator from its first undepressed position to a second depressed position. If the switch assembly is a normally closed switch (i.e., the terminals are electrically coupled by the actuator when the actuator is in its first undepressed position) and the switch assembly terminals are electrically coupled between the tractor engine magneto and an electrical ground of the tractor, the tractor engine is shut off if the operator steps (or falls) off of the tractor seat. That is, the actuator would return to its first undepressed position when the seat is unoccupied, thereby closing the electrical connection between the magneto and electrical ground, resulting in the magneto being grounded out and stalling the engine.
With additional switches and/or relays appropriately mounted and connected, more sophisticated safety functions can be accomplished. For example, the engine may be shut off only if the operator is not sitting on the seat and the tractor""s mowing blade and/or power take off is engaged. U.S. Pat. No. 5,190,019, issued Mar. 2, 1993 and entitled INTERLOCK CIRCUIT FOR DE-ACTIVATING AN ENGINE, also assigned to the assignee of the present invention discloses such a circuit. The ""019 patent is incorporated herein in its entirety by reference.
While the tractor seat pan mounted plunger-type safety switch disclosed in ""502 patent provided a securely mounted switch that was easy to mount, such a switch (and other such prior art seat mounted safety switches) provided only a single circuit (one pole) switch. Additional operational fail-safe safety functions on lawn and garden tractors and riding lawn mowers, such as turning the engine off if the cutting blade is engaged and the tractor is shifted into reverse are desirable. Such additional safety functions create a need for a safety switch having more than one pole, thereby avoiding the necessity of duplicate switches and/or relays. Because of limited mounting room below the seat pan, it is desirable that the switch housing and connector be configured to minimize the height of the assembly extending below the seat pan, that is, along an axis of movement of the actuator. Additionally, it is desirable to prevent an operator from bypassing the operation of the safety functions provided by a seat mounted safety switch by simply disengaging the connector coupled to the switch housing.
The present invention is directed to a three pole plunger switch assembly. The assembly includes a three pole plunger switch and a mating connector. The plunger switch includes a switch housing for supporting components of the plunger switch and a plunger extending into an interior region of the switch housing. The plunger is actuatable from outside the switch housing wherein the plunger is adapted to move between a normal position and an actuated position. The plunger switch includes first, second and third electrically conductive wiper contacts mounted to the plunger for movement with the plunger. First, second and third sets of terminals extend into the switch housing interior region. The first set of terminals includes a first terminal and a second terminal which are electrically coupled by engagement of the first wiper contact in one of the normal and actuated positions of the plunger. The second set of terminals including a third terminal and a fourth terminal which are electrically coupled by engagement of the second wiper contact in one of the normal and actuated positions of the plunger. The third set of terminals including a fifth terminal and a sixth terminal which are electrically coupled by engagement of the third wiper contact in one of the normal and actuated positions of the plunger.
The first, second, third and fourth terminals include outer surface portions that are substantially parallel. The outer surface portions of the first and third terminals are substantially aligned and the outer surface portions of the second and fourth terminals are substantially aligned. The fifth and sixth terminals include outer surface portions that are substantially parallel and transverse to the outer surface portions of the first, second, third and fourth terminals. In one embodiment of the assembly, the fifth and sixth terminal outer surface portions are perpendicular to the outer surface portions of the first, second, third and fourth terminals.
The mating connector includes a connector housing that supports first, second and third sets of terminals. The connector terminals are supported in spaced apart relationship and oriented to electrically connect to the terminals of the first, second and third sets of terminals of the plunger switch when the plunger switch housing and the connector housing are engaged.
Such a three pole terminal configuration of the plunger switch has several advantages. The terminal configuration facilitates use of a single plunger with three support members to support three conductive wiper contacts. The positioning of the three wiper contacts and the three respective sets of terminals provide three wiper contacts paths of travel as the plunger is moved from its normal position to its actuated position. The path of travel of each wiper contact intersects respective pairs of terminals to selectively electrically couple or bridge the pair of terminals comprising each set of terminals in one of either the actuated or normal positions of the plunger.
A set of terminals may be normally open or normally closed. If a set of terminals is normally closed, the wiper contact associated with the terminals bridges the terminals when the plunger is in the normal position and does not bridge the terminals when the plunger is in the actuated position. If a set of terminal is normally open, the wiper contact associated with the terminals bridges the terminals when the plunger is in the actuated position and does not bridge the terminals when the plunger is in the normal position. Advantageously, the plunger wiper support members facilitate two wiper contact mounting positions. The first mounting position is utilized for normally closed terminals and the second mounting position is utilized for normally open terminals.
Another advantage of the terminal configuration of the present invention is that the configuration of the connector and the switch housing terminals prevents engagement of the connector housing and the switch housing in an improper orientation.
These and other objects, advantages and features of the invention will become better understood from a detailed description of an exemplary embodiment of the invention which is described in conjunction with the accompanying drawings.